Radio transmission system



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E. A. HEISING RADIO TRANSMISSION SYSTEM Filed 565,17 29, 1919 m .A mH n4 W; h y /0 Ma d1 9% sic Patented Mar. 25, 1924i.

UNWEED STATES PATENT @FFFHQE.

RAYMOND A. HEISIN G, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, OF N YORK.

EW YORK, N. Y., A CORPORATION OF NEW RADIO TRANSMISSION SYSTEll/I.

Application filed September 29, 1919. Serial No. 327,100.

To all w/mm if may concern:

lie it known that I. RAYMOND A. llnisixc, a citizen of the l'nited States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Radio Transmission Systems, of Which the following is a full, clear, concise, and exact description.

This invention relates to radio transmission systems and more particularly to speech transmittingsystems in which two-way comn'iunicationgmay be attained at each station over a single antenna.

An object of the invention is to prevent production of side tone in a receiver at a radio station by energy from the local transmitter.

A further object of the invention is to control the responsiveness of the receiver and the operationof the transmitter directly by speech or soundenergy without the necessity of manually operating switches.

According to this invention,- a normally operative receiving'set and a normallyinoperative transmitting set are connected to the. same antenna. Voice or sound oper ated relays serve, when energized, to render the receiving set inoperative and to render the transmitting set. operative. A feature of the invention consists in the provision of a normally oscillating oscillator which serves both for the production of oscillations for the transmitter and as a detector; This considerably simplifies the necessary apparatus and makes the control of the system quick acting. I

In the drawing. Fig. 1 illustrates diagramn'iatically a radio telephone. system, and Figs. 2 and 3 illustrate modifications of the system of Fig. 1.

Referring to Fi 1, tuned antenna 1 has associated therewit 1 a thiee-elen1ent vacuum tube 2 in such manner as to constitute an oscillator of well-known type (see for exam ple page 360, volume 38, No. 3 of Proceedings of A. I. E. E.). The space current circuit for the oscillator may be traced from the cathode through space current source 3, normally opened armature 4 of relay 5, contact 6, constant current choke coil 7, high frequency choke coil 8, to the anode of the oscillator. The constant current system of modulation also well known (see Proceedings of 1. E. supra) is employed.

For this, a modulator tube 9 having its anode connected to the anode of the oscillator through high frequency choke coil 8 and its cathode directly connected to the cathode of the oscillator is provided. Choke coil 8 stops currents of the order of the oscillator frequency While freely passing speech and other low frequency currents. Connected inductively to the input circuit of the modulator 9 isa microphone circuit 10 including the usual battery and microphone which serves to impress upon the modulator input circuit electromotive forces coresponding to the sound energy which affects the microphone. A third electron discharge device 11 serves, when subjected to speech current electromotive forces, to permit suiiicient space current to flow in its output circuit to operate electromagnetic relays 5 and 14C in series therewith. Device 11 is therefore termed a relay tube.

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The receiver set comprises a closed circuit tuned to the frequency of the oscillations to be received including inductance coil 12 coupled to the antenna, normally closed armature 13 of electromagnetic relay 1-1, and variable capacity element 15. Connected across the terminals of capacity element 15. through a blocking condenser 16 shunted by a high resistance 17, are the input terminals of a three-element. thermionic detector 18 of well-known type in the output circuit of which a receiver 19 is connected in the ordinary manner. The characters 0, M, It and D are applied to the various tubes in each of the liguresto indicate respectively the oscillator, modulator. relay and detector.

In operation. if no sound energy is impressed upon the microphone, armature t is opened and armature 13 closed as indicated in Fig. 1. Received incoming oscillations are impressed upon the detector and caused to indicate signals in the receiver in the ordinary manner; Oscillator 2 and modulator 9 are both without space current and, accordingly, are inoperative. It follows that. no low frequency or high frequency oscillations will be impressed upon the receiver apparatus by the local transmitter. Slight noises affecting the microphone are insuilicient to cause tube 11 to operate relays 5 and 14. 'hen speech or, other sound waves of considerable energy ati'eet the microphone of circuit 10. relay 1-1 operates, short circuiting the inputcircuit' of detector D and ogening the closed tuned circuit 12, 15. T is prevents side tone in the local receiver 19. At the same time relay 5 is energized and armature 4 closes contact; (3, whereupon the oscillator tube and modulator 9 become active and oscillations modulated in accordance with the sound Waves impressed upon the microphone are radiated from the antenna.

In Fig. 2, the oscillator which is the counterpart of that in Fig. l with the exception of a permanently closed space current circuit, serves also as a detector. This oscillator oscillates continuously. Incoming oscillations are detected by the oscillator tube and yield low frequency signal currents or impulses in its output circuit. For speech transmission, the method disclosed in United States Patent 1330471. patented l chruary 10. 1920, to B. WY. Kendall, is preferably used, that is, the oscillator normally oscillates at the carrier frequency of the incoming oscillations. Connected across the space circuit terminals of oscillator 0 through high frequency choke coil 8 is a path including normally closed armature 20 of relay 21, condenser 22 of suilicient capacity to freely transmit low frequency speech and sound currents, and high reslstance 23. A thermionic amplifier A, preferably of the three-element vacuum tube type, has its input terminals connectedacross resistance 23. and a receivcr 24, connected in its output circuit, accordinglyreproduces-the sounds or speech by which the incoming oscillations are modulated or modified since detected currents of that frequency are applied to the. input circuitof the amplifier. The modulator M is connected as in Fig. 1 to operate according to the constant current method. However, the input circuit of the modulator M is opened at armature 25 of relay 21 and slight sounds are therefore unable tomodulate the oscillations or to cause disturlmnccs to be. repeated into the amplifier input circuit.

In operation. the receiver is normally con nectcd in condition to receive' signals and the oscillator is oscillating. Received oscillations are detected by the oscillator and produce sound indications in receiver 24. If speech or other sound waves of considerable energy are impressed upon the microphone, the s )ace current in vacuum tuhe R is cause to increase. energizing relay 21 which opens the input circuit of amplifier A at 20 and closes that of modulator M at 25. The system is then in operative condition to transmit speech modulated oscillations and the input circuitof the receiver amplifier A is short-eircuitcd through large capacity element 22 by armature 20 closing on its front. contact so as to prevent local side tone.

Fig. 3 illustrates a further modification in which a constantly oscillating oscillator 0 also serves as a detector and the modular tor M is permanently connected to the oscillator O as if for constant current modulation. A polarizing source 26 in the input circuit. of the modulator n'iaintains its grid at such a negative potential with respect to its filament that no space current flows through the tube even when slight sound Waves are applied to its input circuit. In other words, the effect of polarizing source 26 is sufficiently large to overwhelm space current. source 27 so far as the passage of space currentthrough the modulator is concerned. The speech current amplifier A is permanently connected to the secondary winding of a spech current transformer 33, the primary winding of which is in a path including space current source 27 normally connected by armature 2-8 of electromagnetic relay 29 across the'space current electrodes of the modulator and oscillator. The relay tube. R is provided with a blocking condenser. 30 and a high resistance in shunt thereto in its input circuit. The electrical characteristics of these elements are so chosen that speech currents rectified by the input circuit of the relay tube leave a residual negative charge on the grid. This residual charge slowly leaks through the resistance as in the case of detectors operating in this same manner. The characteristics of this tube are such that although the grid is normally maintained at a negative potential by source 26, space current source 27 causes suflicient current to pass through the tube to maintain electromagnetic relay 29 energized, holding its armature 28 closed on its front contact and a second armature 32 open.- If speech waves affect the microphone of circuit. 10, the residual charge on the tube R added to its normal negative potential causes its internal impedance to rise, thus decreasing the space current. Relay 29 accordingly deenergizes permitting armature 32 to close and releasing armature 28 which closes on its back contact. The action of armature 32 closing short'circuits the grid of amplifier A to its cathode, thus renderin the amplifier inoperative to repeat loca disturbances to the receiver. The action of armature 28 in closing on its back contact is to substitute for the space current source 27 and the primary of the transformer 33 a s ace cur rent source 34 of much larger e ectromotive force and constant current choke 35. Source 34 overcomes the efiect of polarizing 'source 26 and drives space current through modulator M. Oscillator O oscillates very vigorously because of the increase inthe B battery potential. system in transmitting speech will be obvious from the foregoing explanation.

Instead of using a tube R of different charzwtcristics from that of tube M, a separate space current source of larger potential The operation of this 1 ,asseoe may be used for this tube or the polarizing source 26 may be connected directly adjacent the grid of the modulator tube and the connection to the elements 30 and 31 may be made from the positive terminal .of the polarizing source.

The relay tube of Fig. 1 operates with normally deenergized electromagnetic relays while that of Fig. 3 operates with normally energized relays. It is to be understood that either form 0 relay circuit may be used in each of the three systems, it being merely necessary to reverse. the posit-ions of the contacts of the various armatures.

As it well known, the general principles governing radio transmission and high frequency carrier current transmission are the same and the application of the features herein disclosed to carrier current transmission falls within the scope of this invention. It is therefore to be understood that although the features of this invention have been disclosed as embodied in particular radio telephone systems, they are not to be limited thereto but only by the -scope of the appended claims.

What is claimed is:

1. In a high frequency transmission system, a high frequency conductor, means connected in energy transfer relation thereto adapted in common for generating high frequency oscillations for transmission and for detecting incoming high frequency oscillations, means for modifying the oscillations generated by said common means in accordance with signals, indicating means associated with said common means and sound control means whereby said system is alternately operative for transmitting signals and for receiving signals.

2. A radio s stem comprising an electric discharge oscil ator and asource of unidirectional current therefor, a switch member movable to different positions to control the application of said unidirectional source to said oscillator, a receiver, means for modifying in accordance with signals the oscillations'produced by said oscillator, a common transmission circuit for transmitting outgoing modifiedoscillations from said oscillator and for transmitting received oscillations to said receiver, and signal operated means for operating said switch member to increase the amplitude of the oscillations produced during transmission.

3. In a high frequency transmission system, a'high frequency conductor, means for producing therein high frequency oscillations, an electron discharge modulator, a space current source therefor, a circuit closing means in the space current circuit of said modulator, a three-element electron discharge receiving tube associated with said high frequency conductor, and sound controlled means for actuating said circuit closer to operative position and applying a short-circuit across the input circuit of said receiving tube.

4. A radio system comprising an antenna, a three-element electron discharge device associated therewith to produce oscillations in said antenna and having input and output circuits, said electrondevicc also constituting a detector of oscillations received bysaid antenna, a modulator and a receiving device associated with said oscillator, and means to alternately close the input circuits of said electron discharge device and receiving device.

5. In combination, anelectron discharge oscillator and an electron discharge modulator, means for applying a coinnmnspace current electromotive force thereto of such value as to cause space. current to flow in said oscillator but not in said modulator, a sound controlled means for increasing the electromotive force applied to said modulator sufficiently to cause space current to flow.

6. A sound controlled relay system comprising an electron discharge device containing a cathode, an anode and an impedance control element, an input circuit connected to said cathode and control element including a capacity element and a high resistance in parallel, an output circuit connected to said anode and cathode and including a normally energized relay coil. and means for applying an alternating electromotive force to said input circuit whereby the energizing current in said coil is decreased.

7. A transmission circuit comprising a sound controlled vacuum tube relay hav ing a cathode, an anode and an impedance control element, an input circuit connected tosaid cathode and control element and including a capacity element and a high resistance in parallel, an output circuit including the winding of an electromagnetic relay, and means for applying a speech current electromotivc force to said input circuit, saidresistance being of such an order of magnitude that the rate of leakage of the negative charge from said control element is slow compared with that of its accumulation during the application of the speech current electromotive force.

8. A radio system comprising an antenna, a three-element electron discharge device for producing oscillations therein during transmission and for detecting oscillations incoming therefrom during reception, an electron discharge modulator associated with said device. alternate space current sources of respectively high and low-elec tromotive force, a double-throw switch for applying said sources alternately to the space circuits of said modulator and device. a receiver operatively associated with said device when the low electromotive force is applied, a relay normally energized to actuate said switch to receiver operative position, and means operated by the modulating impulses for deenergizing said relay whereby said switch is actuated to receiver inoperative position and so as to apply the high electromotive force to said modulator and said device.

9. The system of claim 8 with the addition of a short-circuiting connection across said receiver, said connection containing a circuit closer normally kept open by said relay but closed when said relay is deenergized.

10. A radio system comprising an antenna, means for producing oscillations in said antenna. an electron discharge modulator for modifying said oscillations in accordance with signals, a space current source therefor of suflicient electromotive force to render said modulator operative, means norinally preventing the application of said I source to said modulator, and signal controlled means for applying said source to said modulator. I

11. A radiosystem com rising, at a single station, an electron disciiarge device containing a cathode, an anode and an impedance control element, an input circuit connected to said cathode and control element including a capacity element and a high resistance in parallel and means for applying an audible frequency electromotive force to said input circuit, said resistance being of such an order of magnitude that the rate of leakage of the negative charge from said control element is slow compared with that of its accumulation during the application of said electromotive force.

In witness whereof, I hereunto subscribe my name this 27th day of September ILDQ, 1919.

RAYMOND A. HEISING. 

